Aspartame is one of the most popular artificial sweeteners available on the market. In fact, chances are good that you or someone you know has consumed an aspartame-containing diet soda within the past 24 hours. In 2010, one-fifth of all Americans drank a diet soda on any given day, according to the Centers for Disease Control and Prevention.

While the sweetener remains popular, it’s also faced controversy in recent years. Many opponents have claimed that aspartame is actually bad for your health. There are also claims about long-term repercussions of aspartame consumption.

Unfortunately, while extensive tests have been conducted on aspartame, there’s no consensus as to whether aspartame is “bad” for you.

Aspartame is sold under the brand names NutraSweet and Equal. It’s also used widely in packaged products — especially those labeled as “diet” foods.

The ingredients of aspartame are aspartic acid and phenylalanine. Both are naturally occurring amino acids. Aspartic acid is produced by your body, and phenylalanine is an essential amino acid that you get from food.

When your body processes aspartame, part of it is broken down into methanol. Consumption of fruit, fruit juice, fermented beverages, and some vegetables also contain or result in methanol production. As of 2014, aspartame was the largest source of methanol in the American diet. Methanol is toxic in large quantities, yet smaller amounts may also be concerning when combined with free methanol because of enhanced absorption. Free methanol is present in some foods and is also created when aspartame is heated. Free methanol consumed regularly may be a problem because it breaks down into formaldehyde, a known carcinogen and neurotoxin, in the body. However, the Food Standards Agency in the United Kingdom states that even in children who are high consumers of aspartame, the maximum intake level of methanol is not reached. They also state that since eating fruits and vegetables is known to enhance health, methanol intake from these sources is not a high priority for research.

Dr. Alan Gaby, MD, reported in Alternative Medicine Review in 2007 that aspartame found in commercial products or heated beverages may be a seizure trigger and should be evaluated in cases of difficult seizure management.

A number of regulatory agencies and health-related organizations have weighed in favorably on aspartame. It’s gained approval from the following:

U.S. Food and Drug Administration (FDA)

United Nations Food and Agriculture Organization

World Health Organization

American Heart Association

American Dietetic Association

In 2013, the European Food Safety Authority (EFSA) concluded a review of more than 600 datasets from aspartame studies. It found no reason to remove aspartame from the market. The review reported no safety concerns associated with normal or increased intake.

At the same time, artificial sweeteners have a long history of controversy. Aspartame was developed around the time the FDA banned the artificial sweeteners cyclamate (Sucaryl) and saccharin (Sweet’N Low). Lab tests showed that massive doses of these two compounds caused cancer and other disorders in laboratory animals.

While aspartame is indeed approved by the FDA, the consumer advocate organization Center for Science in the Public Interest has cited numerous studies that suggest problems with the sweetener, including a study by the Harvard School of Public Health.

In 2000, the National Institutes of Health decided saccharin could be removed from the list of cancer-causing substances. Though cyclamate is available in more than 50 countries, it’s not sold in the United States.

Whenever a product is labeled “sugar-free,” that usually means it has an artificial sweetener in place of sugar. While not all sugar-free products contain aspartame, it’s still one of the most popular sweeteners. It’s widely available in a number of packaged goods.

Some examples of aspartame-containing products include:

diet soda

sugar-free ice cream

reduced-calorie fruit juice

gum

yogurt

sugarless candy

Using other sweeteners can help you limit your aspartame intake. However, if you want to avoid aspartame altogether, you’ll also need to make sure to look out for it in packaged goods. Aspartame is most often labeled as containing phenylalanine.

According to the American Cancer Society, aspartame is approximately 200 times sweeter than sugar. So only a very small amount is needed to give food and beverages a sweet flavor. The acceptable daily intake (ADI) recommendations from the FDA and EFSA are:

FDA: 50 milligrams per kilogram of body weight

EFSA: 40 milligrams per kilogram of body weight

A can of diet soda contains about 185 milligrams of aspartame. A 150-pound (68-kilogram) person would have to drink more than 18 cans of soda a day to exceed the FDA daily intake. Alternately, they’d need nearly 15 cans to exceed the EFSA recommendation.

However, people who have a condition called phenylketonuria (PKU) shouldn’t use aspartame. People who are taking medications for schizophrenia should also avoid aspartame.

Phenylketonuria

People with PKU have too much phenylalanine in their blood. Phenylalanine is an essential amino acid found in protein sources such as meat, fish, eggs, and dairy products. It’s also one of the two ingredients of aspartame.

People with this condition aren’t able to properly process phenylalanine. If you have this condition, aspartame is highly toxic.

Tardive dyskinesia

Tardive dyskinesia (TD) is thought to be a side effect of some schizophrenia medications. The phenylalanine in aspartame may precipitate the uncontrolled muscle movements of TD.

Other

Anti-aspartame activists claim there’s a link between aspartame and a multitude of ailments, including:

Research is ongoing to confirm or invalidate connections between these ailments and aspartame, but currently there is still inconsistent outcomes in studies. Some research reports increased risk, symptoms or disease acceleration, while others report no negative outcomes with aspartame intake.

When it comes to diabetes and weight loss, one of the first steps many people take is to cut empty calories from their diets. This often includes sugar.

Aspartame has both pros and cons when considering diabetes and obesity. First, the Mayo Clinic states that, in general, artificial sweeteners may be beneficial for those with diabetes. Still, this doesn’t necessarily mean that aspartame is the best sweetener of choice — you should ask your doctor first.

Sweeteners may also help weight loss efforts, but this is usually only the case if you consume a lot of sugar-containing products before trying to lose weight. Switching from sugary products to those containing artificial sweeteners may also reduce the risk of cavities and tooth decay.

According to a 2014 PLoS One study, rats that were fed aspartame had lower body masses overall. One caveat to the results was that these same rats also had more gut bacteria as well as increased blood sugar. This increase in blood glucose was also linked to insulin resistance.

The research is far from conclusive about how aspartame and other nonnutritive sweeteners affect these diseases and others.

The controversy over aspartame continues. Available evidence doesn’t suggest long-term negative effects, but research is ongoing. Before you switch back to sugar (which is high in calories and has no nutritional value), you can consider natural alternatives to aspartame. You may try sweetening foods and beverages with: